OPTICAL SYSTEMS DESIGN
DOC ID: 10118101
OSD2512 OPERATOR MANUAL
PAGE 90
This page allows you to configure the Port Security Limit Control system and port
settings.
Limit Control allows for limiting the number of users on a given port. A user is
identified by a MAC address and VLAN ID. If Limit Control is enabled on a port, the
limit specifies the maximum number of users on the port. If this number is exceeded,
an action is taken. The action can be one of the four different actions as described
below.
The Limit Control module utilizes a lower-layer module, Port Security module, which
manages MAC addresses learnt on the port.
The Limit Control configuration consists of two sections, a system- and a port-wide.
SYSTEM CONFIGURATION
Mode
Indicates if Limit Control is globally enabled or disabled on the switch. If globally disabled,
other modules may still use the underlying functionality, but limit checks and corresponding
actions are disabled.
Aging Enabled
If checked, secured MAC addresses are subject to aging as discussed under Aging Period.
Aging Period
If Aging Enabled is checked, then the aging period is controlled with this input. If other
modules are using the underlying port security for securing MAC addresses, they may have
other requirements to the aging period. The underlying port security will use the shorter
requested aging period of all modules that use the functionality.
The Aging Period can be set to a number between 10 and 10,000,000 seconds.
To understand why aging may be desired, consider the following scenario: Suppose an end-
host is connected to a 3rd party switch or hub, which in turn is connected to a port on this
switch on which Limit Control is enabled. The end-host will be allowed to forward if the limit
is not exceeded. Now suppose that the end-host logs off or powers down. If it wasn't for aging,
the end-host would still take up resources on this switch and will be allowed to forward. To
overcome this situation, enable aging. With aging enabled, a timer is started once the end-host
gets secured. When the timer expires, the switch starts looking for frames from the end-host,
and if such frames are not seen within the next Aging Period, the end-host is assumed to be
disconnected, and the corresponding resources are freed on the switch.
PORT CONFIGURATION
The table has one row for each port on the switch and a number of columns, which are:
Port
The port number to which the configuration below applies.
Mode
Controls whether Limit Control is enabled on this port. Both this and the Global Mode must
be set to Enabled for Limit Control to be in effect. Notice that other modules may still use the
underlying port security features without enabling Limit Control on a given port.
